Problem(s) Encountered:

The guider software MaximDL was not working since the beginning of the night.  The software is frozen and we were unable to terminate the program using the task manager or command line. We decided not to prioritize guiding and didn't try to restart the computer. 

Solution:

After chasing some false leads, problem was found to be a failing power supply for the guide camera.  A spare power supply was put inline, resolving the issue.